Rooftop Race was a virtual representation of one of Altaïr Ibn-La'Ahad's genetic memories, relived by Desmond Miles in 2012 through the Animus.
Altaïr met with an informant who told Altaïr that one of his colleagues has found some information on Sibrand, although the Assassin would have to track him on his own.
Altaïr approached the informant on a rooftop.
- Informant: I hear you're looking for information on Sibrand. Karn's found something you'd probably find useful. Best track him down if you want it.
Altaïr raced across the city's rooftops and found the other informant.
- Karn: Safety and peace, brother. I've been looking everywhere for you. I stole this letter earlier today. Read it over, hopefully it'll be of use.
Altaïr acquired a letter, which stated Sibrand was soon to return to his private vessel.
Altaïr speaking with the informant
Altaïr racing across the rooftops
Altaïr speaking with the second informant